1. Field of The Invention
The invention relates to forming fabrics used in papermaking machines.
2. Brief Description of The Prior Art
Papermaking machines are well known in the art. The modern papermaking machine is in essence a device for removing water from the paper furnish. The water is removed sequentially in three stages or sections of the machine. In the first or forming section, the furnish is deposited on a moving forming wire and water drained through the wire to leave a paper sheet or web having a solids content of circa 18 to 25 percent by weight. The formed web is carried into a wet press felt section and passed through one or more nip presses on a moving press felt to remove sufficient water to form a sheet. This sheet is transferred to the dryer section of the papermaking machine.
On papermaking machines, endless belts are employed in the various sections to carry the sheet or web. One form of belt which has been used extensively as a forming wire in the forming section of the papermaking machine is one fabricated from an open, multi-layer weave of synthetic, polymeric resin monofilaments. Such fabrics generally perform well in the forming section although there are certain limitations. For example, in the multi-layered weaves there is a tendency for the dry content of the sheet of forming paper to decrease after the last point of vacuum application on the machine, just prior to transfer of the sheet to the wet-press section of the machine. This decrease in dry content is termed "rewet". It is theorized that multiple layer forming fabrics carry water within the weave geometry and that as the sheet of formed paper is carried by the forming fabric beyond the last vacuum application, water migrates back into the carried sheet from the forming fabric.
The forming fabrics of the invention minimize or eliminate the "rewet" phenomena and are therefore advantageous in promoting overall drying efficiency in the forming section of a papermaking machine.